The invention relates to an implant. In particular, the invention relates to a bone screw like a lag screw to be received in a transverse through bore in a bone nail or hip plate.
An implant and particularly a bone implant include a portion or section or end which is adapted to be firstly introduced into a body during an implantation. In the description below, such a portion or section or end is referred to as leading portion or leading section or leading end. Consequently, an opposite portion or section or end of the implant is adapted to be introduced last, wherein this portion or section or end may additionally be configured for an engagement of a tool for inserting the implant into the body. Below, such a portion or section or end is referred to as trailing portion or trailing section or trailing end.
A bone implant may be a pin or a nail or screw or plate. A bone nail may be an intramedullary nail, for example a femur nail, a humerus nail or a tibia nail. A bone screw may be a screw for fixing fragments of a bone fracture or may be a locking screw for locking a bone nail in the bone.
However, due to the anatomical variation of bones it may happen that the trailing end of a bone implant extends out of a bone after implant placement. The trailing end of the implant may act as an interface with an implantation tool and may thus be provided with an appropriate structure like, for example, slots for controlling the forces applied during implant insertion and removal. It may occur that patients complain about pain after surgery in this area, especially when the implant is extending out of the bone. This pain may be caused by sharp edges at the trailing end of the implant. Such edges may cause irritation and/or injury to the surrounding soft tissue.
A migration of a hip screw is reported in the case report “Hip screw lateral migration with no cut-out or non-union implication: a case report” of Nikolaos Lasanianos et al. (Case Journal 2009, 2:6419). A similar report can be found in “Medial pelvic migration of the lag screw in a short gamma nail after hip fracture fixation: a case report and review of the literature” of Xinning Li et al. (Journal of Orthopaedic Surgery and Research 2010, 5:62).